High temperature elastomers from linear poly (silarylene-siloxane-acetylene)

ABSTRACT

A linear polymer has repeating units represented by the formula 
                 
 
wherein
         (a) n is an integer greater than or equal to 0,   (b) x is an integer greater than or equal to 1, and 
                 
    represents an unconjugated acetylenic group when x is equal to 1 or conjugated acetylenic groups when x is greater than 1;   (c) Ar is an aromatic group, and   (c) R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7  and R 8  are independently selected from the group consisting of alkyl, aryl, alkylaryl, haloalkyl, haloaryl, and mixtures thereof. The linear polymer may be thermally cured to form a crosslinked polymer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of application Ser. No.09/625,271, filed Jul. 25, 2000, now U.S. Pat. No. 6,362,289.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to linear polymers that can be cured toform high temperature elastomers and plastics, and in particular to ahigh temperature elastomer made by curing linearpoly(silarylene-siloxane-acetylene).

2. Description of the Related Art

The aerospace industry has a continuing demand for high performancematerials that can withstand extreme variations of temperatures. Inparticular, there is a need for materials that have elastomericproperties, that have thermal, thermo-oxidative and hydrolytic stabilityat high temperatures (as high as 300-350° C.) and that maintain theirflexibility below ambient temperatures. For example, fuel tanks of highflying airplanes and space vehicles require sealants that maintainelasticity for up to 10,000 hours of use at temperatures that range from−60° C. to 400° C. Further, the material must resist swelling whencoming into contact with jet fuel and must have excellent adhesion toand inertness toward metallic substrates.

Linear polymers and crosslinked polymers that have repeating units madeup of diacetylene groups and siloxane groups are disclosed in, forexample, U.S. Pat. No. 5,563,181 to Keller et al and U.S. Pat. No.5,874,514 to Keller et al, both incorporated herein by reference.

Linear polymers and crosslinked polymers and copolymers made up ofsilarylene and siloxane units are disclosed in, for example, U.S. Pat.No. 5,578,380 to Babu, U.S. SIR No. H1612 to Rhein et al, and U.S. Pat.No. 5,346,980 to Babu, all incorporated herein by reference.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a linearpolymer can be crosslinked to form a polymer that has elastomericproperties, that is thermally and oxidatively stable at hightemperatures and that maintains its elastomeric properties at lowtemperatures.

Another object of the present invention is to provide a crosslinkedpolymer that has elastomeric properties.

Another object of the present invention is to provide a crosslinkedpolymer that is thermally and oxidatively stable at temperatures as highas 300-350° C.

Another object of the present invention is to provide a crosslinkedpolymer that maintains its elastomeric properties at temperatures as lowas −50° C.

Another object of the present invention is to provide a linear polymermade by a method of synthesis wherein the mechanical properties of thelinear polymer and of a crosslinked polymer obtained from curing thelinear polymer can be controlled.

These and other objects are obtained by linear polymer that hasrepeating units represented by the formula

wherein

-   -   (a) n is an integer greater than or equal to 0,    -   (b) x is an integer greater than or equal to 1, and    -    represents an unconjugated acetylenic group when x is equal to        1 or conjugated acetylenic groups when x is greater than 1;    -   (c) Ar is an aromatic group, and    -   (c) R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are independently selected        from the group consisting of alkyl, aryl, alkylaryl, haloalkyl,        haloaryl and mixtures thereof.

The invention is further directed to crosslinked polymers by curing alinear polymer as described above.

In the linear polymers and crosslinked polymers of the presentinvention, the acetylenic groups in the backbone of the polymer providefor crosslinking in comparison to polymers that only havesilarylene-siloxane groups. The aromatic groups in the backbone of thepolymer provide for improved thermal stability and rigidity, incomparison to polymers that only have siloxane and acetylene groups.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description of the invention is provided to aidthose skilled in the art in practicing the present invention. However,the following detailed description of the invention should not beconstrued to unduly limit the present invention. Variations andmodifications in the embodiments discussed may be made by those ofordinary skill in the art without departing from the scope of thepresent inventive discovery.

The invention relates to a linear inorganic-organic hybrid polymer and acrosslinked polymer derived therefrom. The linear polymer is made up ofrepeating units represented by the formula

wherein

-   -   (a) n is an integer greater than or equal to 0,    -   (b) x is an integer greater than or equal to 1, and    -    represents an unconjugated acetylenic group when x is equal to        1 or conjugated acetylenic groups when x is greater than 1;    -   (c) Ar is an aromatic group, and    -   (c) R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are independently selected        from the group consisting of alkyl, aryl, alkylaryl, haloalkyl,        haloaryl and mixtures thereof.

Particular values for n and x, and particular choices for the sidechains R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and the aromatic group Ar may beselected according to particular properties desired for the linearpolymer and for elastomers and plastics made using the compound. Forexample, increasing the relative number of silarylene and siloxane units(increasing n) increases the chain flexibility. As discussed in moredetail below, the relative amount of silarylene-siloxane units andacetylene units in the repeating unit (as represented by the value of nin the formula) can be controlled by selecting the relative molaramounts of reactants in one of the steps of the synthesis of thepolymer. Using larger alkyl groups for the side chains R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸ increases the solubility of the linear polymer in organicsolvents and increases the hydrophobicity and decreases thethermo-oxidative stability of elastomers and plastics made using thecompound. Using aryl groups for the side chains R¹, R², R³, R⁴, R⁵, R⁶,R⁷, R⁸ increases the stiffness and slightly increases thethermo-oxidative stability of polymers made using the compound. Usinglarger aryl linking groups for Ar adds stiffness to elastomers andplastics made from the compound. Linear polymers with larger conjugatedacetylenic groups (x greater than 2) are more easily cured, but are moreexpensive to produce.

In the most preferred embodiment, the acetylenic group is butadiyne(x=2), the aromatic group is phenylene, and all the R groups are methyl.The repeating units of this embodiment may thus be represented by thefollowing formula:

The linear polymer of the present invention has the advantage of beingextremely easy to process and convert into elastomers and plastics sinceit is, depending on the selection of variables and substituents, eithera liquid at room temperature or a low melting solid and is soluble inmost organic solvents. The linear polymer is thus well-suited to serveas a thermostat polymeric precursor. The linear polymer may be easilyproduced by the method exemplified in the following reaction scheme,which illustrates the synthesis of the most preferred embodiment,Compound 1, wherein the acetylenic group is butadiyne (x=2), thearomatic group is phenylene, and all the R groups are methyl. Thesynthesis may be carried out in a one pot, two step reaction.Hexachlorobutadiene, 2, is reacted with four equivalents ofn-butyllithium to get 1,4-dilithio-1,3 butakiyne, 3.dimethylaminochlorodimethylsilane, 4, is added to the solution to get1,4-bis(dimethylamino-dimethylsilanyl) butadiyne, 5.

Meanwhile, Compound 6 is formed by reacting an excess amount of1,4-bis(hydroxydimethylsilyl)benzene 7 (weak acid) withbis(dimethylamino)dimethylsilane 8 in refluxing toluene. Despite therelative stability of Si—N bonds, they are readily cleaved by acids andvarious organic and inorganic electrophiles.

Compound 1, the linear polymer, is produced by reacting compound 5 andcompound 6.

Different linear polymers represented by Compound 1 may be created byvarying the relative amount of compound 7 and Compound 8 used in thecreation of Compound 6 (thereby changing the value of n, whichrepresents the length of the aromatic disiloxyl/trisiloxy group incompounds 1 and 6). In this manner, linear polymers having differentproperties and processing parameters tailored to specific needs can beeasily created.

The crosslinked polymer is made by thermally curing the linearpolymer 1. Typically, the curing is carried out for a sufficient timeand at a sufficient temperature to allow at least some of the acetylenegroups of the linear polymer react intermolecularly with each other toform a crosslinked network.

EXAMPLES

Having described the invention, the following examples are given toillustrate specific applications of the invention including the bestmode now known to perform the invention. These specific examples are notintended to limit the scope of the invention described in thisapplication.

Example #1 Synthesis of 1,4-Bis-(Dimethylaminodimethylsilyl) butadiyne

A flame dried 250 ml Schlenk flask containing THF (20 ml) was cooled to−78° C. and n-butyl lithium (20 ml of 2.4 M in hexane, 48.0 mmol) wasadded by syringe. After several minutes hexachlorobutadiene (1.88 ml,12.0 mmol) was added dropwise via syringe over a 10 minute period. Aftercompletion of addition, the cold bath was removed and the mixturestirred at room temperature for 3 hours. The resulting,1,4-dilithio-1,3-butadiyne was used without further purification. Theflask was then recooled to −78° C., anddimethylaminodimethylchlorosilane (3.6 ml, 24 mmol) was added bysyringe. The flask was removed from the cold bath and the reactionmixture stirred at room temperature for 16 hours. At this time ¹H NMRanalysis indicated complete disappearance ofdimethylaminodimethylchlorosilane and formation of1,4-bis-(dimethylaminodimethylsilyl)-butadiyne. The THF was removed invacuo, and the mixture was taken up in a minimum amount of pentane andfiltered. The pentane was removed in vacuo to give 2.91 g (96%) of1,4-bis(dimethylaminodimethylsilyl)butadiyne.

Example #2 Synthesis of Silarylene-Siloxane Prepolymer Terminated byHydroxyl Moieties, Where n=1

A three-necked flask was equipped with a stir bar, reflux condenser,inlet and outlet adapters for argon gas. The entire assembly was flamedried. 1,4-Bis(hydroxydimethylsilyl) benzene (5.20 g, 23 mmol) was addedand toluene (15 ml) was injected by syringe followed by the addition ofbis (dimethylamino)dimethylsilane (2.07 ml, 11.5 mmol). The resultingsolution was brought to reflux temperature and maintained until therewas no further evidence of dimethylamine evolution, as determined by amoist litmus paper test on the exhaust stream of the argon outlet. Thereaction mixture was refluxed an additional hour. ³H NMR analysis showedcomplete disappearance of the starting materials and formation of thesilarylene-siloxane prepolymer. The prepolymer was used as prepared andthen chain extended with 1,4-bis(dimethylaminodimethylsilyl)butadiyne(see example #6).

Example #3 Synthesis of Silarylene-Siloxane Prepolymer Terminated byHydroxyl Moieties, Where n=2

A three-necked flask was equipped with a stir bar, reflux condenser,inlet and outlet adapters for argon gas. The entire assembly was flamedried. 1,4-Bis(hydroxydimethylsilyl) benzene (5.65 g, 24.9 mmol) wasadded and toluene (15 ml) was injected by syringe followed by theaddition of bis (dimethylamino)dimethylsilane (3.00 ml, 16.6 mmol). Theresulting solution was brought to reflux temperature and maintaineduntil there was no further evidence of dimethylamine evolution, asdetermined by a moist litmus paper test on the exhaust stream of theargon outlet. The reaction mixture was refluxed an additional hour. ¹HNMR analysis showed complete disappearance of the starting materials andformation of the silarylene-siloxane prepolymer. The prepolymer was usedas prepared and then chain extended with1,4-bis(dimethylaminodimethylsilyl)butadiyne (see example #7).

Example #4 Synthesis of Silarylene-Siloxane Prepolymer Terminated byHydroxyl Moieties, Where n=3

A three-necked flask was equipped with a stir bar, reflux condenser,inlet and outlet adapters for argon gas. The entire assembly was flamedried. 1,4-Bis(hydroxydimethylsilyl) benzene (2.66 g, 11.7 mmol) wasadded and toluene (10 ml) was injected by syringe followed by theaddition of bis (dimethylamino)dimethylsilane (1.59 ml, 8.81 mmol). Theresulting solution was brought to reflux temperature and maintaineduntil there was no further evidence of dimethylamine evolution, asdetermined by a moist litmus paper test on the exhaust stream of theargon outlet. The reaction mixture was refluxed an additional hour. ¹HNMR analysis showed complete disappearance of the starting materials andformation of the silarylene-siloxane prepolymer. The prepolymer was usedas prepared and then chain extended with1,4-bis(dimethylaminodimethylsilyl)butadiyne (see example #8).

Example #5 Synthesis of Linear Poly(Silarylene-Siloxane-Acetylene)Where, n=0 as a Precursor to a High Temperature Plastic

A three-necked flask was equipped with a stir bar, reflux condenser,inlet and outlet adapters for argon gas. The entire assembly was flamedried. 1,4-Bis(hydroxydimethylsilyl) benzene (2.43 g, 10.7 mmol) wasadded. A previously prepared sample of1,4-bis-(dimethylaminodimethylsilyl) butadiyne (2.71 g, 10.7 mmol) wasdissolved in 20 ml of toluene. Part of this solution (16 ml) was addedto the three-necked flask containing the 1,4-bis(hydroxydimethylsilyl)benzene. The remaining 4 ml was diluted to 20 ml with toluene. Afterrefluxing the reaction mixture for 1 hour, an additional amount of the1,4-bis (dimethylaminodimethylsilyl)butadiyne solution (4 ml) was addedat time intervals of 30 to 60 minutes until dimethylamine evolution hadceased. Toluene was removed at reduced pressure and excess ether wasadded. The ether solution was washed with a saturated solution ofaqueous NH₄Cl (2×100 ml). After aqueous workup and extraction withdiethyl ether, the polymeric solution was dried over Na₂SO₄ andfiltered. The solvent was removed in vacuo to give 2.71 g, (65%) of thelinear poly(silarylene-siloxane-acetylene) as a viscous brown liquid.

Example #6 Synthesis of Linear Poly(Silarylene-Siloxane-Acetylene)Where, n=1 as a Precursor to a High Temperature Elastomer

To a three-necked flask containing the previously preparedsilarylene-siloxane prepolymer terminated by hydroxyl moieties (seeexample #2) was added a 19.5 ml aliquot of a 20 ml toluene solutioncontaining 1,4-bis (dimethylaminodimethylsilyl)butadiyne (2.91 g, 11.5mmol). After refluxing the reaction mixture for 1 to 2 hours, anadditional amount of the toluene solution containing1,4-bis(dimethylaminodimethylsilyl)butadiyne (200-500 μl) was added attime intervals of 30 to 60 minutes until the viscosity of the solutionvisibly increased and dimethylamine evolution had ceased. Toluene wasremoved at reduced pressure and excess ether was added. The ethersolution was washed with a saturated solution of aqueous NH₄Cl (2×100ml). After aqueous workup and extraction with diethyl ether, the polymersolution was dried over Na₂SO₄ and filtered. The solvent was removed invacuo to give 4.31 g, (56%) of the linearpoly(silarylene-siloxane-acetylene) as a brown viscous liquid. IR (cm⁻¹)2080 (m), (—C≡C—C≡C—), 1059 (vs, broad), (Si—O). ¹H NMR (CDCl₃, ppm)7.51 (s), (C₆H₄), 0.35 (s), 0.30 (s), 0.29 (s), 0.22 (s), 0.03 (s),(Si(CH₃)₂). ¹³C NMR (CDCl₃, ppm) 140.8, 140.7, 132.3, 132.25, 132.21,(C₆H₄), 86.9, 85.4, (—C≡C—C≡C—), 2.09, 1.36, 0.92, 0.74, 0.59, (SiCH₃)₂).

Example #7 Synthesis of Linear Poly(Silarylene-Siloxane-Acetylene)Where, n=2 as a Precursor to a High Temperature Elastomer

To a three-necked flask containing the previously preparedsilarylene-siloxane prepolymer terminated by hydroxyl moieties (seeexample #3) was added a 19.5 mL aliquot of a 20 ml toluene solutioncontaining 1,4-bis (dimethylaminodimethylsilyl)butadiyne (2.10 g, 8.32mmol). After refluxing the reaction mixture for 1 to 2 hours, anadditional amount of the toluene solution containing1,4-bis(dimethylaminodimethylsilyl)butadiyne (200-500 μl) was added attime intervals of 30 to 60 minutes until the viscosity of the solutionvisibly increased and dimethylamine evolution had ceased. Toluene wasremoved at reduced pressure and excess ether was added. The ethersolution was washed with a saturated solution of aqueous NH₄Cl (2×100mL). After aqueous workup and extraction with diethyl ether, thepolymeric solution was dried over Na₂SO₄ and filtered. The solvent wasremoved in vacuo to give 5.84 g, (88%) of the linearpoly(silarylene-siloxane-acetylene) as a brown viscous liquid. IR (cm⁻¹)2076 (m), (—C≡C—C≡C—), 1053 (vs, broad), (Si—O). ¹H NMR (CDCl₃, ppm)7.50 (s), (C₆H₄), 0.34 (s), 0.27 (s), 0.21 (s), 0.02 (s), (Si(CH₃)₂).¹³C NMR (CDCl₃, ppm) 141.5, 132.9, (C₆H₄) 86.0, 83.1, (—C≡C—C≡C—), 2.08,1.52, 1.03 0.88, 0.67, (Si(CH₃)₂).

Example #8 Synthesis of Linear Poly(Silarylene-Siloxane-Acetylene)Where, n=3 as a Precursor to a High Temperature Elastomer

To a three-necked flask containing the previously preparedsilarylene-siloxane prepolymer terminated by hydroxyl moieties (seeexample #4) was added a 4.0 ml aliquot of a 5.0 ml toluene solutioncontaining 1,4-bis (dimethylaminodimethylsilyl)butadiyne (0.83 g, 3.28mmol). After refluxing the reaction mixture for 1 to 2 hours, anadditional amount of the toluene solution containing1,4-bis(dimethylaminodimethylsilyl)butadiyne (50-100 μl) was added attime intervals of 15 to 30 minutes until the viscosity of the solutionvisibly increased and dimethylamine evolution had ceased. Toluene wasremoved at reduced pressure and excess ether was added. The ethersolution was washed with a saturated solution of aqueous NH₄Cl (2×100ml). After aqueous workup and extraction with diethyl ether, thepolymeric solution was dried over Na₂SO₄ and filtered. The solvent wasremoved in vacuo to give 2.45 g, (67%) of the linearpoly(silarylene-siloxane-acetylene) as a brown viscous liquid. IR (cm⁻¹)2074 (w), (—C≡C—C≡C—), 1052 (vs, broad), (Si—O). ¹H NMR (CDCl₃, ppm)7.50 (s), (C₆H₄), 0.35 (s), 0.30 (s), 0.28 (s), 0.22 (s), 0.02 (s),(Si(CH₃)₂). ¹³C NMR (CDCl₃, ppm) 140.7, 140.2, 132.2, (C₆H₄) 86.9, 85.3,(—C≡C—C≡C—), 2.11, 1.40, 0.96, 0.77, (Si(CH₃)₂).

Example #9 Thermal Curing of the Plastic Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=0 (See Example #5 forSynthesis)

To a platinum thermogravimetric analyzer pan was placed 28.7410 mg ofthe linear poly(silarylene-siloxane-acetylene). The sample was thenheated under an atmosphere of dry nitrogen at 150, 200, 350 and 450° C.for 60, 60, 120 and 120 minutes, respectively. After completion of theisothermal curing experiment the sample was void free and exhibited thecharacteristics of a plastic material.

Example #10 Pure Cure Thermo-Oxidative Stability Study on CrosslinkedPoly(Silarylene-Siloxane-Acetylene) Where, n=0 (See Example #5 forSynthesis and Example #9 for Curing)

Following the isothermal curing cycle performed on the linearpoly(silarylene-siloxane-acetylene), the sample was allowed to cool toambient temperature. The sample was then isothermed on athermogravimetric analyzer for 120 minutes at 200, 250, 300, and 350° C.respectively in an air atmosphere at a flow rate of 50 cc/min. Theplastic sample exhibited excellent oxidative stability over the timeframe of the experiment, experiencing only a 0.17% weight loss, asdetermined by thermogravimetric analysis.

Example #11 Bulk Thermal Curing of the Plastic Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=0 (See Example #5 forSynthesis)

To a circular aluminum pan pretreated with a teflon mold release wasweighed 1.2015 g of the linear poly(silarylene-siloxane-acetylene). Inorder to remove any volatile material, the sample was placed on a hotplate and isothermed at 125° C. under dynamic vacuum conditions.Following the degassing procedure, the sample was placed in a tubefurnace and heated sequentially under an atmosphere of dry argon for 120minutes at 200, 250, 300 and 350° C., respectively. After completion ofthe isothermal curing cycle, the liquid linearpoly(silarylene-siloxane-acetylene) had been transformed to a void free,hard plastic material.

Example #12 Thermal Curing of the Elastomeric Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=1 (See Example #6 forSynthesis)

To a platinum thermogravimetric analyzer pan was placed 53.6410 mg ofthe liquid poly(silarylene-siloxane-acetylene). The sample was thenconverted to an elastomer by heating sequentially under an atmosphere ofdry nitrogen for 120 minutes at 200, 250, 300, 350 and 400° C.,respectively. After completion of the isothermal curing experiment, thesample was void free and exhibited the characteristics of an elastomericmaterial, i.e., soft and flexible.

Example #13 Post Cure Thermo-Oxidative Stability Study on CrosslinkedPoly(Silarylene-Siloxane-Acetylene) Where n=1 (See Example #6 forSynthesis and Example #12 for Curing)

Following the isothermal curing cycle performed on the elastomericprecursor linear poly(silarylene-siloxane-acetylene), the sample wasallowed to cool to ambient temperature. The sample was then isothermedin a thermogravimetric analyzer for 60 minutes at 200 and 250° C. andfor 120 minutes at 300 and 330° C., respectively, in an air atmosphereat a flow rate of 50 cc/min. The sample exhibited excellent oxidativestability over the time frame of the experiment, experiencing only a3.26% weight loss. After completion of the thermo-oxidative study, thesample was visibly void free and still retained flexibility asdetermined by bending the sample.

Example #14 Bulk Thermal Curing of the Elastomeric Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=1 (See Example #6 forSynthesis)

To a circular aluminum pan pretreated with a teflon mold release wasweighed 1.6182 g of the linear poly(silarylene-siloxane-acetylene). Inorder to remove any volatile material, the sample was placed on a hotplate and isothermed at 125° C. under dynamic vacuum conditions.Following the degassing procedure, the sample was placed in a tubefurnace and converted to an elastomer by heating sequentially under anatmosphere of dry argon for 120 minutes at 200, 250, 300 and 350° C.,respectively. After completion of the isothermal curing cycle, theliquid linear poly(silarylene-siloxane-acetylene) had been transformedto a tough, void-free, flexible material.

Example #15 Thermal Curing of the Elastomeric Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=2 (See Example #7 forSynthesis)

To a platinum thermogravimetric analyzer pan was placed 28.9990 mg ofthe liquid linear poly(silarylene-siloxane-acetylene). The sample wasthen heated sequentially under an atmosphere of dry nitrogen for 120minutes at 200, 250, 300, 350 and 400° C. respectively. After completionof the isothermal curing experiment, the sample was void free andexhibited the characteristics of an elastomeric material, i.e., soft andflexible.

Example #16 Post Cure Thermo-Oxidative Stability Study on CrosslinkedPoly(Silarylene-Siloxane-Acetylene) Where n=2 (See Example #7 forSynthesis and Example #15 for Curing)

Following the isothermal curing cycle performed on the liquid precursorlinear poly (silarylene-siloxane-acetylene), the elastomeric sample wasallowed to cool to ambient temperature. The sample was then isothermedin a thermogravimetric analyzer for 60 minutes at 200 and 250° C. andfor 120 minutes at 300 and 330° C., respectively, in an air atmosphereat a flow rate of 50 cc/min. The sample exhibited excellent oxidativestability over the time frame of the experiment, experiencing only a7.69% weight loss. After completion of the thermo-oxidative study, thesample was visibly void-free and still retained flexibility, asdetermined by bending the sample.

Example #17 Bulk Thermal Curing of the Elastomeric Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=2 (See Example #7 forSynthesis)

To a circular aluminum pan pretreated with a teflon mold release wasweighed 1.6203 g of the liquid linear poly(silarylene-siloxane-acetylene). In order to remove any volatilematerial, the sample was placed on a hot plate and heated at 125° C.under dynamic vacuum conditions. Following the degassing procedure, thesample was placed in a tube furnace and converted to an elastomer byheating sequentially under an atmosphere of dry argon for 120 minutes at200, 250, 300 and 350° C., respectively. After completion of theisothermal curing cycle, the liquid linearpoly(silarylene-siloxane-acetylene) had been transformed to a tough,void-free, flexible material.

Example #18 Thermal Curing of the Elastomeric Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=3 (See Example #8 forSynthesis)

To a platinum thermogravimetric analyzer pan was placed 41.6950 mg ofthe liquid linear poly(silarylene-siloxane-acetylene). The sample wasthen converted to an elastomer by heating in sequentially under anatmosphere of dry nitrogen for 120 minutes at 200, 250, 300, 350 and400° C., respectively. After completion of the isothermal curingexperiment, the sample was void-free and exhibited the characteristicsof an elastomeric material, i.e., soft and flexible.

Example #19 Post Cure Thermo-Oxidative Stability Study on CrosslinkedPoly(Silarylene-Siloxane-Acetylene) Where n=3 (See Example #8 forSynthesis and Example #18 for Curing)

Following the isothermal curing cycle performed on the elastomericprecursor linear poly(silarylene-siloxane-acetylene), the sample wasallowed to cool to ambient temperature. The elastomeric sample was thenisothermed in a thermogravimetric analyzer for 60 minutes at 200 and250° C. and for 120 minutes at 300 and 330° C., respectively in an airatmosphere at a flow rate of 50 cc/min. The sample exhibited excellentoxidative stability over the time frame of the excellent, experiencingonly a 3.96% weight loss. After completion of the thermo-oxidativestudy, the sample was visibly void-free and still retained flexibility,as determined by bending the sample.

Example #20 Bulk Thermal Curing of the Elastomeric Precursor: LinearPoly(Silarylene-Siloxane-Acetylene) Where n=3 (See Example #8 forSynthesis)

To a circular aluminum pan pretreated with a teflon mold release wasweighed 1.6053 g of the linear poly(silarylene-siloxane-acetylene). Inorder to remove any volatile material, the sample was placed on a hotplate and isothermed at 125° C. under dynamic vacuum conditions.Following the degassing procedure, the sample was placed in a tubefurnace and converted to an elastomer by heating sequentially under anatmosphere of dry argon for 120 minutes at 200, 250, 300 and 350° C.,respectively. After completion of the isothermal curing cycle, theliquid linear poly(silarylene-siloxane-acetylene) had been transformedto a tough, void-free, flexible material.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

1. A crosslinked polymer made by a process comprising the step ofthermally curing a linear polymer that comprises repeating unitsrepresented by the formula

wherein (a) n is an integer greater than or equal to 0, (b) x is aninteger greater than or equal to 1, and

 represents an unconjugated acetylenic group when x is equal to 1 orconjugated acetylenic groups when x is greater than 1; (c) Ar is anaromatic group, and (c) R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ areindependently selected from the group consisting of alkyl, aryl,alkylaryl, haloalkyl, haloaryl and mixtures thereof.
 2. The crosslinkedpolymer of claim 1 wherein x is
 2. 3. The crosslinked polymer of claim 1wherein Ar is phenylene.
 4. The crosslinked polymer of claim 1 whereinR¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are CH₃.
 5. The crosslinked polymer ofclaim 1 wherein n is
 0. 6. The crosslinked polymer of claim 1 wherein nis
 1. 7. The crosslinked polymer of claim 1 wherein n is
 2. 8. Thecrosslinked polymer of claim 1 wherein n is
 3. 9. A crosslinked polymermade by a process comprising the step of thermally curing a linearpolymer that comprises repeating units represented by the formula

wherein n is an integer greater than or equal to 0, and R¹, R², R³, R⁴,R⁵, R⁶, R⁷ and R⁸ are independently selected from the group consistingof alkyl, aryl, alkylaryl, haloalkyl, haloaryl and mixtures thereof. 10.A crosslinked polymer made by a process comprising the step of thermallycuring a linear polymer that comprises repeating units represented bythe formula

wherein n is an integer greater than or equal to
 0. 11. The crosslinkedpolymer of claim 10 wherein n is
 0. 12. The crosslinked polymer of claim10 wherein n is
 1. 13. The crosslinked polymer of claim 10 wherein n is2.
 14. The crosslinked polymer of claim 10 wherein n is
 3. 15. Acrosslinked polymer made by a process comprising the steps of (a)reacting hexachlorobutadiene with n-butyl lithium to form1,4-dilithio-1,3-butadiyne, (b) reacting the 1,4-dilithio-1,3-butadiyneof step (a) with (dimethylamino) (R⁹-disubstituted)chlorosilane, whereineach R⁹ independently selected from the group consisting of alkyl, aryl,alkylaryl, haloalkyl, haloaryl and mixtures thereof, to form1,4-bis(dimethylamino, R⁹-disubstituted-silyl)butadiyne, (c) reacting1,4- bis(hydroxy-R¹⁰-disubstituted-silyl)-Ar, wherein Ar is an aromaticgroup, wherein R¹⁰ is selected from the group consisting of alkyl, aryl,alkylaryl, haloalkyl, haloaryl and mixtures thereof, withbis(dimethylamino)R¹¹-disubstituted-silane, wherein R¹¹ is selected fromthe group consisting of alkyl, aryl, alkylaryl, haloalkyl, haloaryl andmixtures thereof, to form a prepolymer of the formula:

wherein n is an average value greater than or equal to 0, and whereinthe value of n is controlled by selecting the initial molar ratio of1,4- bis(hydroxy-R¹⁰-disubstituted-silyl)benzene Ar and bis(dimethylamino)R¹¹-disubstituted-silane, (d) reacting the prepolymer ofstep (c) with the 1,4-bis(dimethylamino,R⁹-disubstituted-silyl)butadiyne of step (b) to form a linear polymer,and (e) thermally curing the linear polymer of step (d).
 16. Thecrosslinked polymer of claim 15 wherein Ar is phenylene.
 17. Acrosslinked polymer made by a process comprising the steps of (a)reacting hexachlorobutadiene with n-butyl lithium to form1,4-dilithio-1,3-butadiyne, (b) reacting the 1,4-dilithio-1,3-butadiyneof step (a) with (dimethylamino)dimethylchlorosilane to form1,4-bis(dimethylaminodimethylsilyl)butadiyne, (c) reacting1,4-bis(hydroxydimethylsilyl)benzene withbis(dimethylamino)dimethylsilane, to form a prepolymer of the formula:

wherein n is an average value greater than or equal to 0, and whereinthe value of n is controlled by selecting the initial molar ratio of1,4-bis(hydroxydimethylsilyl)benzene andbis(dimethylamino)dimethylsilane, (d) reacting the prepolymer of step(c) with the 1,4-bis(dimethylaminodimethylsilyl)butadiyne of step (b) toform the a linear polymer, and (e) thermally curing the linear polymer.